The dubious history of the heredity environment controversy can be easily traced as far back as the start of the present century with at least some historical evidence placing the roots of this dispute in the time of John Locke. This controversy has continued despite continual reiteration that the critical question is not how much of a trait is due to heredity and how much is due to environment, but rather how environment transact to influence development." ( Wachs , 1983, p. 386).
This paper will focus on the nature/nurture controversy and the extent to which an individuals intellectual level is determined either by inborn intelligence or by environmental factors.
The relative powers of nature and nurture have been actively pursed by psychologists and biologists striving to determine how heredity and environment influence the development of intelligence.
Before we can go on to discuss the relationships between intelligence and the controversy that exists between the different schools of thought regarding inherited or environmental issues we must have an understanding of what intelligence really is.
Of all the words used in pressed day psychology, intelligence is one of the most difficult to define and is also one of the most controversial. There is however, a general agreement that intelligence refers to the overall faculties of the mind which concern themselves with the sorting of information in the brain after it has been received by the senses, the perceiving of relationships between this new data and information which is already in memory, and the capacity to make rapid and appropriate decisions as a result of the previous processes.
The intellectual faculties of the brain are dynamic and interactive and relate to the capacity of the central nervous system to respond speedily and appropriately in a rapidly changing and potentially threatening environment. Raymond J. Corsini provides us with a somewhat more simplistic definition of the term intelligence. According to Corsini (1984) the term intelligence can be employed to indicate the amount of knowledge available and the rapidity with which new knowledge is acquired; the ability to adapt to new situations and to handle concepts, relationships, and abstract symbols. While the heredity/environment topic continues to be a controversial issue, a great deal of evidence has been gathered to support both arguments. In order to investigate the topic of nature/nurture it is important to consider a variety of research elements. Among these elements are some of the most relevant issues pertaining to this subject including: twin, adoption, family, orphanage life, IQ, and race studies. It is to these studies we will now turn our attention.
The importance of twin studies is evident if we look at the studies objectively, if intelligence is basically hereditary, identical twins who have the same genetic legacy, should be concordant for that trait than are fraternal twins, which are no more alike genetically than other siblings. Burt's (1958) famous study show that the intelligence test scores of identical twins, whether reared together or apart , display considerably higher correlation than the scores of fraternal twins.
Burt's work is currently viewed with caution due to the manner in which he gathered and interpreted his data (Vernon, 1979). However, Burt's research provides an important foundation for this research.
Jone's study (1946) shows that there is a modest difference in the intelligence test scores of twins reared apart, and the more divergent the environments, the greater the difference.
"While environmental factors are important in raising or lowering a child's level of intellectual performance, these studies demonstrate that they only do so within limits set by heredity." (Mussen, Conger, and Kagon, 1963...